Separable plasma torch apparatus

ABSTRACT

Plasma torch apparatus having separable parts such as separable inlet head and/or feed device. Preferably the head and base are made of brass.

L A N Y L B M A H L M.

SEPARABLE PLASMA TORCH APPARATUS 2 Sheets-Sheet l Filed Oct. 14, 197019, 1972 s. M. l.. HAMBLYN ETAL 3,706,652

SEPARABLE PLASMA TORCH APPARATUS 2 Sheets-Sheet 2 Filed Oct. 14, 1970STPA/EN M10/@K [5167 #f4/W62 //V ANTHONY PA TfQ/C/ MOA/5V JAN MAL COL/WM/QCA//NNON JOHN EDM/ND 79077-5? INVENTORS.

United States atent O 3,706,652 SEPARABLE PLASMA TORCH APPARATUS StephenMark Lesley Hamblyn, Long Ditton, Anthony Patrick Money, Surbiton, IanMalcolm Mackinnon, Kingston-upon-Thames, and John Edmund Trotter,Hampton, England, assignors to United States Borax & ChemicalCorporation, Los Angeles, Calif.

Filed Oct. 14, 1970, Ser. No. 80,691 Claims priority, application GreatBritain, May 20, 1970, 24,495/ 70 Int. Cl. B01k 1/00 U.S. Cl. 204-312 11Claims ABSTRACT OF THE DISCLOSURE Plasma torch apparatus havingseparable parts such as separable inlet head and/or feed device.Preferably the head and base are made of brass.

This invention relates to an improved apparatus for effecting ahightemperature chemical reaction, namely a plasma torch.

In co-pending application Ser. INo. 737,464, liled June 17, 1968, by H.D. Murdoch and S. M. L. Hamblyn, now Pat. No. 3,625,846 issued Dec. 7,1971, there is described a process for carrying out a high-temperaturechemical reaction, such as between boron trichloride and hydrogen, toproduce nely divided elemental boron, in which one gaseous reactant isionized by induction heating to form a plasma and another generallygaseous reactant is fed into the plasma as that reaction takes place. Inthat application there is also described an apparatus for use in theprocess which in essence is a quartz tube surrounded by an inductioncoil, having an inlet upstream of the coil for the gas to be ionized andhaving a number of quartz tubular inlets downstream of the coil throughwhich the second reactant is introduced to the plasma.

In a related co-pending application Ser. No. 1,195, led Jan. 7, 1970, byS. M. L. Hamblyn, A. P. Money, and I. M. Mackinnon, is described animproved apparatus according to said earlier application, which isprovided with a jacket through which a fluid cooling medium may bepassed.

We have now devised a novel plasma torch which is an improvement in thetorch described in the aboveidentified copending applications.

According to the present invention, the plasma torch comprises a quartztube which is surrounded by an induction coil and within which a plasmais formed as gases pass along the tube, an inlet device for gas upstreamof the coil, and a feed device for reactant downstream of the coil,either the inlet device or the feed device or, preferably, both being anelement removably attached to the tube.

Thus if supply tubes for plasma forming gas or for reactant to thereaction tubes are damaged, they can be more readily replaced. Thisconstruction of separable parts facilitates access to the reaction tubefor cleaning.

Preferably each removable element is made of a material stronger thanquartz which is not heated by electromagnetic induction; the preferredsuch material being brass. Thus, the apparatus comprises as separableelements, a gas inlet head, a reaction tube, and a reactant feed device.

The inlet device is suitably a cylindrical head of a strong,para-magnetic material such as brass, having substantially the sameradial cross-section as the reaction tube, closed at one end by anintegral cap, and bored to provide at least one tangential entry portfor gas. Its open end can then be compressively urged into sealingPatented Dec. 19, 1972 ICC contact, e.g., through a compressible sealmember with the upstream end of the reaction tube. The head can beprovided with an integral cooling jacket.

The feed device is suitably an annular element of strong, para-magneticmaterial such as brass, of internal crosssection substantially the sameas the radial cross-section of the reaction tube. This too can becompressively urged into sealing contact with the open downstream end ofthe reaction tube. This annular element is bored to provide at least oneinlet passage for reactant, and preferably has a number of such passagecircumferentially spaced and radially inwardly directed. There can bemore than o ne such annular element, for the'entries of differentreactants. They or each annular element can be provided with passagesfor coolant, either by having an integral jacket or, preferably, by thepresence of a cooling passage formed in the solid material from whichthe annular element is shaped.

A plasma torch according to the invention will now be described, by wayof example, with reference to the accompanying drawings, in which:

FIG. l shows a longitudinal section through a plasma torch, thecomponents being shown detached from each other in position forassembly;

FIG. 2 shows a transverse section of a head of the torch taken alongA-A1;

FIG. 3 shows a plan, viewed from upstream, of the rst base; and

FIG. 4 shows a plan, also viewed from upstream, of the second base.

In FIG. l there is shown a cylindrical quartz reaction tube 10 which issurrounded by a cylindrical quartz jacket 11 joined to the reaction tubeby a flange 12 which extends radially outwardly from the downstream endof the reaction tube. Interposed between the reaction tube and thejacket is a cylindrical quartz battle 13, extending upstream beyond thejacket and downstream substantially to the flange. The bal-lie is joinedcircumferentially to the reaction tube at the upstream end 14 and thejacket is joined circumferentially to the bafiie at the upstream end 15.The jacket has near its upstream end a conduit 16 for the admission ofcoolant water to the cooling channel 17 formed between the jacket andbarile; and the baie has near its upstream end a conduit 18 for the exitof coolant water from a cooling channel 17A formed between the bailleand the reaction tube, the two cooling channels being in communicationat their downstream ends. The tube assembly of reaction tube, bai-lleand jacket is surrounded by a radio frequency induction coil 19. In theposition of operation the coil is xed in an operating bay (not shown)and the tube assembly can be slid into the coil or removed therefrom asnecessary.

A gas injection head, indicated generally at 20, is provided to matewith the upstream end .14 of the reaction tube. An inner cylindricalbrass member 21 of the head, substantially the same diameter as tube 10,is provided with a flange 22 which extends radially outwardly at itsdownstream end and with a brass disc 23 which closes its upstream end.Four gas inlet ports 24, equally spaced from the brass disc andequi-angularly disposed about the circumference of the inner member areformed in the inner member, being directed to admit gas substantially ata tangent to the interior of the head. A ange 25 is provided around theupstream end of the inner member below the inlet ports, the flange 25extending radially outwardly from the inner member and being returnedupstream of the brass disc. The Outer face 26 of the returned portion ofthe flange 25 is threaded to cooperate with a brass cap 27 which isapertured to receive a centrally located conduit 28 for gas and which,together with the inner member, disc and flange 25, detnes a manifold29.

A cylindrical brass jacket 30 is welded to lflanges 22 and 25 andcontains a downstream inlet port 31 and an upstream outlet port 32 forcoolant water.

A base assembly, indicated generally at 33 and shown in detail in FIGS.3 and 4 is provided to seat on the downstream end of the reaction tube.A brass annular base 34, having in its upstream surface a central recess35 to provide a concentric circular housing for the tube assembly,contains a concentric circular manifold 36; manifold 36 communicateswith the exterior of the base via two diametrically opposed tail gasinlets 37 and communicates with an internal passage 38 (which is alignedwith the interior of tube via eight passages 39, which are equiangularlydisposed about the inner circumference of the manifold and extendradially inward from the manifold, being cranked to enter passage 38 atdischarge port 40, directed towards the head at an angle to the axis ofthe tube. The base also contains upstream a concentric circular duct 41into which an inlet passage 42 and a diametrically opposed outletpassage 43 pass; duct 41 is used as a cooling channel.

Base 34 is, in turn, on a second brass annular base 44 which contains adownstream concentric circular manifold 45 communicating with twodiametrically opposed secondary tail gas inlets 46 and leading into acentral annular orifice 47 by means of eight passages 48, equiangularlydisposed about the inner circumference of the manifold and extendingradially inward from the manifold, being cranked to enter the orice atdischarge port 49, directed towards the head at an angle to the axis ofthe tube. The second base also contains four solids feed pipes 50, eachleading from the periphery of the base to the annular orifice and beingequi-angularly disposed about the circumference of an annular orifice.

To assemble the apparatus of this invention, ring 34 is urged againstring 44 in the position shown in FIG. l with gasket 51 interposed, whilering 44 is in alignment with a conduit for the removal and cleaning ofgases. Tube 10l with its associated water jackets is similarly urgedagainst ring 33, being received within recess 35 and spaced from thering by the gasket 52, and the head is urged in the position shown inFIG. l against the upstream end of tube lil, a gas-tight seal beingformed by the interposed O-ring 53. The assembled apparatus is held inposition by clamps which urge head 10 against ring 44.

In use of the apparatus, gas to be ionised, such as an argon-hydrogenmixture, is delivered through inlet 28 into head 20` and then passesthrough the tube 10, being ionised to form a plasma when passing throughthe tube within RF coil 19. A reactant to be reacted with the plasma isfed into the downstream end of the plasma through one or both of therings 34, 44. For example, boron trichloride gas can be fed throughinlet 37 or through inlet 46. If it is desired to react a solidreactant, this is suitably delivered through inlet 50. One can, forexample, make elemental cobalt by blowing cobalt chloride (III) as asolid powder suspended in argon gas into a hydrogen plasma. Theoperation of a chemical process in apparatus of the sort described inthe present application is more fully described in our co-pendingapplication No. 737,464 or British Pat. 1,194,415.

In a typical run Nickel (II) chloride in a stream of boron trichloride(1:2 molar ratio) is passed through inlets 50 of the ring at a rate of27 g./min. Hydrogen s passed through inlet 28 of the .ring ata rate of40 liters per minute. The resultant product is nickel boride. Thereaction is particularly good if the nickel chloride has a particle sizeof 60 microns or less.

During use of the apparatus it is cooled by passage of a refrigerant,e.g. water, through cooling channels 32, or 18, or 411. The product ofthe reaction is deposited on the walls of the apparatus as a ne powder,or may be carried by unreacted gases out of the apparatus into theremoval conduit and thence to separation apparatus such as a bagiilterafter which the gases are Washed. Being made of separable parts theapparatus can readily be undone to permit removal of deposited powderproduct and to permit cleaning. The apparatus is stronger than quartz sothere is less ranger of damage to the coolant tubes or to the inletmeans for reactant, and if there is damage then the damaged detachablepart can be replaced without having to replace the entire apparatus.

Various changes and modifications of the invention can be made and, tothe extent that such variations incorporate the spirit of thisinvention, they are intended to be included within the scope of theappended claims.

What is claimed is:

1. A plasma torch apparatus comprising a quartz tube adapted for forminga plasma as gases pass along within said tube, an induction coilsurrounding said quartz tube, an inlet device for gas removably attachedto said quartz tube upstream of said induction coil, and means forfeeding reactant attached to said quartz tube downstream of saidinduction coil, said inlet device comprising a cylindrical head made ofa para-magnetic material, having substantially the same radialcross-section as said quartz tube, an integral cap enclosing one endthereof, the opposite end being compressively urged into sealing contactwith the upstream end of said quartz tube, said head being provided withat least one tangential entry port for gas.

2. A torch apparatus of claim 1 in which said means for feeding reactantis removably attached to said quartz tube.

3. The plasma apparatus according to claim 1 wherein said head isprovided with four entry ports equi-angularly spaced in said cylindricalhead, said entry ports cornmunicating with a chamber defined by theclosed end of said cylindrical head and a cap surrounding the closedend, said cap having a conduit for gas.

4. The torch apparatus according to claim 2 in which both said inletdevice and said means for feeding reactant are made of brass.

5.. The apparatus according to claim 1 in which said para-magneticmaterial is brass.

6. The apparatus according to claim 1 in which said cylindrical head issurrounded by an integral cooling jacket.

7. The apparatus according to claim 2 in which said means for feedingreactant comprises an annular element of para-magnetic material havingan internal cross-section substantially the same as the radialcross-section of said quartz tube and having at least one inlet passagefor reactant, said reactant feeding means being compressively urged intosealing contact with the downstream end of said quartz tube.

8. The apparatus according to claim 7 in which said para-magneticmaterial is brass.

9. The apparatus according to claim 7 in which said inlet passage forreactant comprises more than one radially inwardly directed passagescircumferentially spaced in said means for feeding reactant.

|10. The apparatus according to claim 7 in which said annular element isprovided with passages for coolant.

11. The apparatus according to claim 9 in which said means for feedingreactant is a base assembly comprising an upper and lower annular basein sealed relationship and being aligned with a conduit for removal andcleaning of gases.

References Cited UNITED STATES PATENTS 3,547,802 12/l97;0 Gleit et al.204-312 3,345,280 lll/1967 `Berghaus 204-164 JOHN H. MACK, PrimaryExaminer T. TUFARIELLO, Assistant Examiner

